| Dental bonding agents provide the link between a fixed prosthesis and the supporting prepared tooth structure. Traditionally, zinc phosphate cement has been the most popular material, despite its well-documented disadvantages, particularly solubility and lack of adhesion. Therefore, many alternative materials have been introduced and glass ionomer cement (QIC) is one of them.Glass ionomer cements are very popular in clinical treatment, principally because they combine the inherent ability to release fluoride with the desirable characteristics of biocompatibility and adhesion to tooth structure. Although used as restorative materials, cavity liners, and bonding cements, early glass ionomer materials had unfavorable physical properties such as poor wear resistance, brittleness, low compressive strength, poor esthetics, and sensitivity to moisture contamination, especially its great susceptibility to contamination by moisture. Contacting with water at an early stage during setting changes the setting reaction of GICs, which will change the cement properties.Objectives: The study was to assess the solubility of four GICs by Paffenbarger's weight test, to determine whether pH of solution has any influence on the solubility behavior of GICs, to evaluate the GICs immersed in distilled water at early stages after mixing. And to evaluate the influence of protective agent on the water solubility of GICs with the Oilo's weight test.Materials and Methods: (1) Specimen preparation: 120 standardize flat discs (diameter of 15mm, thickness of 1mm) were fabricated in performed dies according to each manufacturer's specification. The discs were divided into four groups of thirty and described as S group, F group, D group, A group. (2) Model preparation: Resin molds with two circular cavities (diameter of 5mm, depth of 3mm) were fabricated by Oilo's methods. (3) Specimens were desiccated to a constant mass and then placed in distilled water, artificial saliva and lactic acid. The weight changes of the specimens were measured using an electronic analytical balance. (4) The changes of solubility of four GIC contacting with water at different time during the initial setting period. The procedure was divided two groups according to whether using protecting agent or not. (5) Statistical analysis was executed by SPSS 10.0 Software, significant level =0.05.Results: (1) The pH of solution seems to have an influence on the solubility behavior of some GICs. S group and D group has higher solubility in lactic acid than in distilled water and artificial saliva(P<0.05). However, there was no difference among three solutions in F group and D group(P>0.05). (2) Increasing the time from the start of mixing until immersion in water from 3 to 9 minutes resulted in a marked decrease i n 1 oss o f substance from the surface o f a 11 four c ements. The d ecrease i n solubility was greater between the 3- and 6-minute immersion times that recorded between t he 6 - a nd 9-minute i mmersion t ime(P<0.05). T he 1 owest c ement 1 oss w as recorded for Fuji II cement after 9 minutes immersion time(0. 63mg/cm2 ). The greatest loss was for Aqua lonofil cement after 3 minutes immersion time(13.33mg/cm2). For all of the observed adhesive cements, Densply cement showed the lowest mean loss of substance at 3 to 6 minutes immersion time. However, the loss of Densply cement was higher than Fuji cement at 9 minutes immersion time(.P<0.05). (3) Compared with the former results, the solubility of four GICs protected with petroleum jelly decreased significantly after 6 minutes immersion time(P<0.05). However, after 3 minutes immersion time, only Densply cement show significant difference between protected and unprotected groups(P<0.05), no significant difference shown among other three materials. And after 9 minutes immersion time, the solubility of Shanghai cement and Aqua lonofil cement decreased significantly due to using protecting agent, no significant difference shown among other two GICs.Conclusions: (1) pH of the solution has no signi...
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